No big deal, but kinda keep it down. Don't play a radio out loud. Kinda talk in hushed tones after 10 pm. You know, generally enjoy the sounds of nature and let others do the same.
Breathing is quite important. It is especially important to actively avoid causing another hiker an asthmatic emergency in a wilderness setting, far from medical care. If you must smoke, please remove yourself completely from the group so others cannot smell or otherwise be exposed to the fumes from your cigarette or e-cig.
Our adventures are for humans only. Dogs are not allowed on the trails in many of the places we hike, and since we cross jurisdictions sometimes, we could start on a trail that allows dogs, then cross into a region that does not. Aside from the legal concern, dogs can be disruptive to local wildlife and some hikers have fears or allergies. Of course your pooch is the nicest, sweetest, most adorable and lovable mammal on the planet. You can love him up when you get home.
Of course you want to be available for emergency phone calls and if something important comes up, by all means, take the call. Aside from that, please silence your cell or turn it off and appreciate being disconnected from the city. You staying disconnected helps you and your group tune in to the adventure. Also, cell phones don't usually work in wilderness settings so you won't be tempted.